This invention relates in general to a laser method of scribing graphics on materials including fabrics, leathers, vinyls, rubber, wood, metals, plastics, ceramics, glass and other materials (hereinafter collectively referred to as the xe2x80x9cmaterialsxe2x80x9d). The term xe2x80x9cscribexe2x80x9d, as used herein, means to contact the material with a laser beam to form a graphic. The term xe2x80x9cgraphicxe2x80x9d, as used herein, refers to decorative and artistic designs, nondecorative designs, patterns, graphic images, looks such as a sandblasted look, a stonewashed look and a frayed look, alphanumeric characters, logos, other identification, and any other visual composition scribed by the laser on a material. In a preferred embodiment, this invention relates to a laser method of scribing graphics on fabrics, leathers and vinyls.
Materials have commonly been used to make, without limitation, clothing, linens, footwear, belts, purses and wallets, luggage, vehicle interiors, furniture coverings, wall coverings and many other manufactured goods. Graphics have been formed on these materials to give them a unique and attractive appearance.
The typical methods of forming graphics on materials are various methods of dyeing, printing, weaving, embossing and stamping. Unfortunately, such methods are very costly in terms of capital investment and operating cost, and they are often plagued with environmental problems.
Complex and intricate graphics are often-more-attractive than simple graphics. However, there has previously been no cost efficient method of forming complex and intricate graphics on the materials. Most of the previous methods lack the necessary registration and precision to insure that minute details of the graphics are accurately and repeatably presented on the materials.
Lasers have been used in the fabric industry to cut fabrics into separate pieces. They have also been used to engrave designs on carpets, and to fix dyes or heat treat unbleached or bleached goods so as to impart improved adhesion properties. However, in the past, certain technical barriers have prevented the use of lasers to form graphics on fabric, leather and vinyl materials. When such use was attempted, the laser beam caused complete carbonization, burnthrough and/or melting at the point of contact. This resulted in burning, complete penetration and/or the formation of an undesirable hole or defect in the material.
If the technical barriers could be overcome, a laser would be a desirable method of forming graphics on materials. For one thing, a laser is well adapted for forming complex and intricate graphics on materials with precision and repeatability. Moreover, laser manufacturing methods are speedy and cost efficient, and they do not cause environmental problems. Thus it would be desirable to provide a suitable method of using a laser to form graphics on materials.
This invention relates to a unique laser method of scribing graphics on materials. In the method, a laser beam contacts a material and alters the physical and/or chemical properties of the material to scribe a graphic. The keys to the invention are: 1) the identification and understanding of a new energy measurement called Energy Density Per Unit Time (hereinafter referred to as xe2x80x9cEDPUTxe2x80x9d), and 2) the identification and simultaneous control of the laser operating parameters which influence EDPUT. Once a range of EDPUT is determined for scribing a desired graphic on a given material, the EDPUT can be controlled to stay within that range to achieve desired results in a repeatable fashion. In a preferred embodiment, the invention relates to a method of scribing graphics on fabric, leather and vinyl materials. In this embodiment, the EDPUT can be controlled to substantially avoid complete carbonization, melting and/or burnthrough of the material. Thus, the invention can overcome the technical barriers which have prevented the use of lasers to scribe graphics on such materials in the past.
The operating parameters include the continuous power of the laser beam, the area of the spot formed by the laser beam on the material, and the speed of the laser beam relative to the surface of the material. These parameters each and in an interactive manner influence the EDPUT which is the critical factor to eliminate complete carbonization, burnthrough and/or melting, yet produce a visible graphic on the material. If the EDPUT is too large, the laser will carbonize, burn through or melt through the material. Conversely, if the EDPUT is too small, the graphic scribed onto the material will not be sufficiently visible. Preferably, EDPUT is defined as follows:       EDPUT    ⁢          xe2x80x83        ⁢          (              watts        ⁢                  -                ⁢        sec        ⁢                  /                ⁢                  mm          3                    )        =            (                        Continuous          ⁢                      xe2x80x83                    ⁢          Power          ⁢                      xe2x80x83                    ⁢                      (            watts            )                                    Area          ⁢                      xe2x80x83                    ⁢          of          ⁢                      xe2x80x83                    ⁢          Spot          ⁢                      xe2x80x83                    ⁢                      (                          mm              2                        )                              )        ⁢          (              1                  Speed          ⁢                      xe2x80x83                    ⁢                      (                          mm              ⁢                              /                            ⁢              sec                        )                              )      
It was found that the preferred EDPUT was different for different types of materials, and was often different for different colors and weights of material. Further, it was found that the preferred EDPUT was often different for different types and sizes of graphic scribed onto the material. This invention then teaches the importance of identifying and simultaneously controlling several laser operating parameters together so as to achieve an EDPUT which produces the desired results each and every time.
Accordingly, this invention teaches the use of a variable power laser such that the continuous power can be ratcheted down or up to certain levels. Previous literature typically refers to the use of a laser having a specific power output, for example a 75 watt YAG laser or a 25 watt CO2 laser. In contrast, this invention teaches to control the continuous power and other variables simultaneously and within specific limits so that the EDPUT is within a range to produce the desired results. Consequently, although a 25 watt CO2 laser was used in experiments relating to this invention, the continuous power was controlled such that power levels between 0.25 and 25 watts were achievable.
This invention also introduces a wav to influence the EDPUT by changing the area of the spot formed on the material by the laser beam. Typically, previous literature refers to focused laser radiation. However, it was found that the area of the spot can be increased and the EDPUT reduced by defocusing the laser beam both at distances greater than and less than the focus distance between the laser lens and the material. The invention also teaches how to produce specific graphics by oscillating the laser beam along a waveform such as a sawtooth or semicircle. In several cases, the best way to achieve desired results was by oscillating the laser beam at distances which were out of focus.
New graphics can be imparted onto materials at the point of sale retail location, wholesale warehouse or manufacturing plant which are not possible by any other means, thereby creating new products with expanded market opportunities. In particular, a variety of desirable graphics can be produced on denim fabric and on leather/vinyl by the laser method of the invention. The graphics on denim fabric include, without limitation, graphic images, logos and identification, a sandblasted look, a stonewashed look, a frayed look, a threadbare look and a stitched look. Intricate laser induced graphics can be imparted onto leather and vinyl where unique graphics are seldom found. The graphics on leather and vinyl include, without limitation, graphic images, a tufted look, a hand sewn look, and logos and identification.
The products made by this method maintain the quality of the graphic following repeated washings. In some experiments, it was found that graphics were visible before washing (particularly for denim), but following one or repeated washings the graphic either faded away or caused tears in the material. It was particularly critical then to: 1) conduct computer designed experiments to identify the specific combination of laser operating parameters which produced the desired EDPUT, and 2) evaluate the graphic following several washings.
The laser method of this invention can be used to impart identification unique to each piece of material. The registration and precision necessary to repeatedly scribe alphanumeric characters on a garment or piece of goods can be controlled very accurately, once the preferred EDPUT is identified and controlled for that material and type of identification. Further, the computer can be programmed to increment the identification number by one so that the shoes, jeans, shirts, or other garment or goods can be quickly and uniquely identified in a somewhat automatic manner by simply positioning the first piece under the laser and pressing the start button, positioning the second piece under the laser and pressing the start button, etc. This technology can then find wide application in garment or goods identification for inventory control, quality control, counterfeiting prevention and product labeling.
The graphics can be produced on materials very cost efficiently with modern automatic laser systems. The EDPUT for the particular kind of material and graphic can be easily controlled by computer. The laser method of forming graphics avoids the costs associated with a heavy investment in capital equipment and environmental protection equipment. No preprocessing of the material such as soaking or spraying is required prior to scribing with the laser beam.